(Have you an idea of how long does it take to confirm this kind of "low-fees" transaction ?

Best regards,

As achow pointed out, you have to wait for the transactions into your address to confirm before you can send tese other transaction. For a fast transaction, you should check the recommendation in my previouspost of the https://bitcoinfees.21.co/ website.

You can always ask the users here as there are at least three transactions that need confirming here so asking users here might make it a bit faster.